Method and apparatus for colour imaging a three-dimensional structure

ABSTRACT

A device for determining the surface topology and associated color of a structure, such as a teeth segment, includes a scanner for providing depth data for points along a two-dimensional array substantially orthogonal to the depth direction, and an image acquisition means for providing color data for each of the points of the array, while the spatial disposition of the device with respect to the structure is maintained substantially unchanged. A processor combines the color data and depth data for each point in the array, thereby providing a three-dimensional color virtual model of the surface of the structure. A corresponding method for determining the surface topology and associate color of a structure is also provided.

CROSS-REFERENCE

This application is a continuation of U.S. application Ser. No.13/620,159, filed on Sep. 14, 2012, which is a continuation of U.S.application Ser. No. 13/333,351, filed on Dec. 21, 2011, now U.S. Pat.No. 8,363,228, which is a continuation of U.S. application Ser. No.12/770,379, filed on Apr. 29, 2010, now U.S. Pat. No. 8,102,538, whichis a continuation of U.S. application Ser. No. 12/379,343, filed on Feb.19, 2009, now U.S. Pat. No. 7,724,378, which is a continuation of U.S.application Ser. No. 11/889,112, filed on Aug. 9, 2007, now U.S. Pat.No. 7,511,829, which is a continuation of U.S. application Ser. No.11/154,520, filed on Jun. 17, 2005, now U.S. Pat. No. 7,319,529, anapplication claiming the benefit under 35 U.S.C. §119(e) of U.S.Provisional Application No. 60/580,109, filed on Jun. 17, 2004, andclaiming the benefit under 35 U.S.C. §119(e) of U.S. ProvisionalApplication No. 60/580,108, filed on Jun. 17, 2004, the contents of eachof which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to optical scanners, particularly forproviding a digital representation of three-dimensional objectsincluding color. The invention finds particular application in thesurveying of the intraoral cavity.

BACKGROUND OF THE INVENTION

Many methods have been developed for obtaining the three dimensionallocation of surface points of an object, for a host of applicationsincluding, inter alia, the intraoral cavity. Techniques for directnon-contact optical measurement, in particular for direct opticalmeasurement of teeth and the subsequent automatic manufacture ofdentures, are known. The term “direct optical measurement” signifiessurveying of teeth in the oral cavity of a patient. This facilitates theobtainment of digital constructional data necessary for thecomputer-assisted design (CAD) or computer-assisted manufacture (CAM) oftooth replacements without having to make any cast impressions of theteeth. Such systems typically include an optical probe coupled to anoptical pick-up or receiver such as charge coupled device (CCD) and aprocessor implementing a suitable image processing technique to designand fabricate virtually the desired product. Such methods include, forexample, confocal imaging techniques as described in WO 00/08415assigned to the present assignee. These methods provide a digitalthree-dimensional surface model that is inherently monochromatic, i.e.,no color information is obtained in the imaging process.

Associating color information with three-dimensional objects is notstraightforward, particularly when the position information is obtainedby using a three dimensional scanning method, while the colorinformation is obtained by using a two dimensional scanning method. Theproblem of conformally mapping the two dimensional color informationonto the three dimensional surface model is difficult and it is commonfor mismatching of the color with three-dimensional points to occur.Essentially, where two-dimensional color detectors are used forobtaining the color information, it is difficult to accurately associatecolor information from the detectors with the correct points on thethree dimensional surface model, particularly where relative movementbetween the object and the device occurs between the acquisition of thethree-dimensional topological data and acquisition of thetwo-dimensional image data.

EP 837 659 describes a process and device for obtaining a threedimensional image of teeth. Three-dimensional surface data is obtainedby first covering the surface with an opaque, diffusely reflectingmaterial, and the object is illuminated with monochromatic light. Theimage of the object under the layer is obtained by the process describedin U.S. Pat. No. 4,575,805 using intensity pattern techniques. In orderto obtain a two-dimensional color image of the object, the reflectinglayer has to be removed. The method thus requires the camera to bemanually re-aligned so that the two-dimensional color image should moreor less correspond to the same part of the object as the threedimensional image. Then, the three dimensional image may be viewed on ascreen as a two-dimensional image, and it is possible to superimpose onthis two-dimensional image the two-dimensional color image of the teethtaken by the camera.

U.S. Pat. No. 6,594,539 provides an intraoral imaging system thatproduces images of a dental surface, including three dimensional surfaceimages and also two dimensional color images, with the same camera.

In U.S. Pat. No. 5,440,393, the shape and dimensions of a dentalpatients mouth cavity including upper and lower tooth areas and the jawstructure, are measured by an optical scanner using an externalradiation source, whose reflected signals are received externally andconverted into electronic signals for analysis by a computer. Bothsurface radiation and reflection from translucent internal surfaces arescanned, and processing of reflections may involve a triangulationsystem or holograms.

In U.S. Pat. No. 5,864,640, a scanner is described having a multipleview detector responsive to a broad spectrum of visible light. Thedetector is operative to develop several images of a three dimensionalobject to be scanned. The images are taken from several relative angleswith respect to the object. The images depict several surface portionsof the object to be scanned. A digital processor, coupled to thedetector, is responsive to the images and is operative to develop with acomputational unit 3-D coordinate positions and related imageinformation of the surface portions of the object, and provides 3-Dsurface information that is linked to color information without need toconformally map 2-D color data onto 3-D surface.

Of general background interest, U.S. Pat. No. 4,836,674, U.S. Pat. No.5,690,486, U.S. Pat. No. 6,525,819, EP 0367647 and U.S. Pat. No.5,766,006 describe devices for measuring the color of teeth.

SUMMARY OF THE INVENTION

In accordance with the present invention, a device and method fordetermining the surface topology and color of at least a portion of athree dimensional structure is provided. Preferred non-limitingembodiments of the invention are concerned with the imaging of athree-dimensional topology of a teeth segment, optionally including suchwhere one or more teeth are missing. This may allow the generation ofdata for subsequent use in design and manufacture of, for example,prosthesis of one or more teeth for incorporation into said teethsegment. Particular examples are the manufacture of crowns, bridgesdental restorations or dental filings. The color and surface data isprovided in a form that is highly manipulable and useful in manyapplications including prosthesis color matching and orthodontics, amongothers.

The determination of the 3D surface topology of a portion of athree-dimensional structure is preferably carried out using a confocalfocusing method, comprising:

(a) providing an array of incident light beams propagating in an opticalpath leading through a focusing optics and a probing face; the focusingoptics defining one or more focal planes forward said probing face in aposition changeable by said optics, each light beam having its focus onone of said one or more focal plane; the beams generating a plurality ofilluminated spots on the structure;

(b) detecting intensity of returned light beams propagating from each ofthese spots along an optical path opposite to that of the incidentlight;

(c) repeating steps (a) and (b) a plurality of times, each time changingposition of the focal plane relative to the structure; and

(d) for each of the illuminated spots, determining a spot-specificposition, being the position of the respective focal plane, yielding amaximum measured intensity of a respective returned light beam; andbased on the determined spot-specific positions, generating datarepresentative of the topology of said portion.

The determination of the spot-specific positions in fact amounts todetermination of the in-focus distance. The determination of thespot-specific position may be by measuring the intensity per se, ortypically is performed by measuring the displacement (S) derivative ofthe intensity (I) curve (dI/dS) and determining the relative position inwhich this derivative function indicates a maximum intensity. The term“spot-specific position (SSP)” will be used to denote the relativein-focus position regardless of the manner in which it is determined. Itshould be understood that the SSP is always a relative position as theabsolute position depends on the position of the sensing face. Howeverthe generation of the surface topology does not require knowledge of theabsolute position, as all dimensions in the cubic field of view areabsolute.

The SSP for each illuminated spot will be different for different spots.The position of each spot in an X-Y frame of reference is known and byknowing the relative positions of the focal plane needed in order toobtain maximum intensity (namely by determining the SSP), the Z or depthcoordinate can be associated with each spot and thus by knowing theX-Y-Z coordinates of each spot the surface topology can be generated.

In order to determine the Z coordinate (namely the SSP) of eachilluminated spot the position of the focal plane may be scanned over theentire range of depth or Z component possible for the measured surfaceportion. Alternatively the beams may have components, each of which hasa different focal plane. Thus, by independent determination of SSP forthe different light components, e.g. 2 or 3 with respectivecorresponding 2 or 3 focal planes, the position of the focal planes maybe changed by the focusing optics to scan only part of the possibledepth range, with all focal planes together covering the expected depthrange. Alternatively, the determination of the SSP may involve a focalplane scan of only part of the potential depth range and for illuminatedspots where a maximum illuminated intensity was not reached, the SSP isdetermined by extrapolation from the measured values or othermathematical signal processing methods. Thus, in each case, a Z-value isobtained for each point along an X-Y grid representing a plurality oflight beams. In this manner, a three-dimensional (3D) numerical entity Emay be crated, comprising a plurality of coordinates (X, Y, Z)representative of the surface topology of the object being scanned.

Alternatively, any other suitable method may be employed to obtain the3D entity E.

According to the present invention, a two dimensional (2D) color imageof the 3D structure that is being scanned is also obtained, buttypically within a short time interval with respect to the 3D scan.Further, the 2D color image is taken at substantially the same angle andorientation with respect to the structure as was the case when the 3Dscan was taken. Accordingly, there is very little or no substantialdistortion between the X-Y plane of 3D scan, and the plane of the image,i.e., both planes are substantially parallel, and moreover substantiallythe same portion of the structure should be comprised in both the 3Dscan and the 2D image. This means that each X-Y point on the 2D imagesubstantially corresponds to a similar point on the 3D scan having thesame relative X-Y values. Accordingly, the same point of the structurebeing scanned has substantially the same X-Y coordinates in both the 2Dimage and the 3D scan, and thus the color value at each X, Y coordinateof the 2D color scan may be mapped directly to the spatial coordinatesin the 3D scan having the same X, Y coordinates, wherein to create anumerical entity I representing the color and surface topology of thestructure being scanned.

Where the X, Y coordinates of the color image do not preciselycorrespond to those of the 3D scan, for example as may arise where oneCCD is for the 3D scanning, while another CCD is used for the 2D colorimage, suitable interpolation methods may be employed to map the colordata to the 3D spartial data.

To provide a more accurate mapping, it is possible to construct a 2Dimage along the X-Y plane of the 3D model, and using procedures such asoptical recognition, manipulate the color 2D image to best fit over this3D image. This procedure may be used to correct for any slightmisalignment between the 2D color scan and the 3D scan. Once the color2D image has been suitably manipulated, the color values of the color 2Dimage are mapped onto the adjusted X-Y coordinates of the 3D scan.

Thus the present invention provides a relatively simple and effectiveway for mapping 2D color information onto a 3D surface model.

The present invention thus provides a device and method for obtaining anumerical entity that represents the color and surface topology of anobject. When applied particularly to the intraoral cavity, the device ofthe invention provides advantages over monochrome 3D scanners, includingsuch scanners that are based on confocal focusing techniques. Forexample, the 2D color image capability on its own enables the dentalpractitioner to identify the area of interest within the oral cavitywith a great degree of confidence in order to better aim the device forthe 3D scanning. In other words, an improved viewfinder is automaticallyprovided. Further, rendition of a full color 3D image of the target areacan help the practitioner to decide on the spot whether the scan issufficiently good, or whether there are still parts of the teeth or softtissues that should have been included, and thus help the practitionerto deciode whether or not to acquire another 3D color entity.

Creation of a color 3D entity that is manipulable by a computer isextremely useful in enabling the practitioner to obtain data from suchan entity that is useful for procedures carried out in the dentalcavity.

Thus, according to the present invention, a device is provided fordetermining the surface topology and associated color of at least aportion of a three dimensional structure, comprising:

scanning means adapted for providing depth data of said portioncorresponding to a two-dimensional reference array substantiallyorthogonal to a depth direction;

imaging means adapted for providing two-dimensional color image data ofsaid portion associated with said reference array;

wherein the device is adapted for maintaining a spatial disposition withrespect to said portion that is substantially fixed during operation ofsaid scanning means and said imaging means. In other words, operation ofthe scanning means and the imaging means is substantially or effectivelysimultaneous in practical terms, and thus the actual time interval thatmay exist between operation of the two means is so short that theamplitude of any mechanical vibration of the device or movement of theoral cavity will be so small as can be ignored.

The device is adapted for providing a time interval between acquisitionof said depth data and acquisition of said color image data such thatsubstantially no significant relative movement between said device andsaid portion occurs. The time interval may be between about 0 seconds toabout 100 milliseconds, for example 5, 10, 20, 30, 40, 50, 60, 70, 80,90 or 100 milliseconds, and preferably between about 0 to about 50milliseconds, and more preferably between about 0 and 20 milliseconds.

The device further comprise processing means for associating said colordata with said depth data for corresponding data points of saidreference array. In described embodiments, the operation of saidscanning means is based on confocal imaging techniques. Such scanningmeans may comprise:

a probing member with a sensing face;

first illumination means for providing a first array of incident lightbeams transmitted towards the structure along an optical path throughsaid probing unit to generate illuminated spots on said portion alongsaid depth direction, wherein said first array is defined within saidreference array;

a light focusing optics defining one or more focal planes forward saidprobing face at a position changeable by said optics, each light beamhaving its focus on one of said one or more focal plane;

a translation mechanism for displacing said focal plane relative to thestructure along an axis defined by the propagation of the incident lightbeams;

a first detector having an array of sensing elements for measuringintensity of each of a plurality of light beams returning from saidspots propagating through an optical path opposite to that of theincident light beams;

a processor coupled to said detector for determining for each light beama spot-specific position, being the position of the respective focalplane of said one or more focal planes yielding maximum measuredintensity of the returned light beam, and based on the determinedspot-specific positions, generating data representative of the topologyof said portion.

The first array is arranged to provide depth data at a plurality ofpredetermined spatial coordinates substantially corresponding to thespatial disposition of said incident light beams.

The first illumination means comprises a source emitting a parent lightbeam and a beam splitter for splitting the parent beam into said arrayof incident light beams. The first illumination means may comprise agrating or microlens array.

The device may comprise a polarizer for polarizing said incident lightbeams are polarized. Further, the device may comprise a polarizationfilter for filtering out from the returned light beams light componentshaving the polarization of the incident light beams.

The illumination unit may comprise at least two light sources and eachof said incident beams is composed of light components from the at leasttwo light sources. The at least two light sources emit each a lightcomponent of different wavelength. The light directing optics defines adifferent focal plane for each light component and the detectorindependently detects intensity of each light components.

The at least two light sources may be located so as to define opticalpaths of different lengths for the incident light beams emitted by eachof the at least two light sources.

Typically, the focusing optics operates in a telecentric confocal mode.Optionally, the light directing optics comprises optical fibers.

Typically, the sensing elements are an array of charge coupled devices(CCD). The detector unit may comprise a pinhole array, each pinholecorresponding to one of the CCDs in the CCD array.

The operation of said imaging means may be based on:

illuminating said portion with three differently-colored illuminationradiations, the said illuminations being combinable to provide whitelight,

capturing a monochromatic image of said portion corresponding to eachsaid illuminating radiation, and

combining the monochromatic images to create a full color image,

wherein each said illuminating radiation is provided in the form of asecond array of incident light beams transmitted towards the portionalong an optical path through said probing unit to generate illuminatedspots on said portion along said depth direction, wherein said secondarray is defined within said reference frame.

The second array is arranged to provide color data at a plurality ofspatial coordinates substantially corresponding to the spatialcoordinates of said first array. The device may comprise colorillumination means adapted for providing three second illuminatingradiations, each of a different color. The color illumination meanscomprises second illumination means for providing said three secondilluminating radiations, each of a different color. Alternatively, thecolor illumination means comprises second illumination means forproviding two said second illuminating radiations, and wherein saidfirst illumination means provides another said second illuminatingradiation each said second illuminating radiation being of a differentcolor. Optionally, each one of said second illumination radiations is adifferent one of red, green or blue light. The second illumination meansmay comprise radiation transmission elements that are configured to belocated out of the path of said light beams or said returned light beamat least within said light focusing optics. The probing member may bemade from a light transmissive material having an upstream opticalinterface with said light focusing optics and a reflective face forreflecting light between said optical interface and said sensing face.The second illumination means may be optically coupled to said opticalinterface for selectively transmitting illuminating radiations in atleast two colors to said portion via said sensing face. The colorillumination means may comprise second illumination means for providingtwo said second illuminating radiations, and wherein said firstillumination means provides another said second illuminating radiationeach said second illuminating radiation being of a different color. Theprobing member may comprise a removable sheath having an inner surfacesubstantially complementary to an outer surface of said probing member,and having a window in registry with said sensing face, wherein saidsheath is made from a waveguiding material and is adapted to transmitsaid light from said second illuminating means from an upstream facethereof to a downstream face associated with said window. The secondillumination means may be optically coupled to said upstream face forselectively transmitting said second illuminating radiations in at leasttwo colors to said portion via said downstream face. Preferably, thesheath is disposable after use with a patient.

In another embodiment, the reflective face comprises a dichroic coating,having relatively high reflectivity and low optical transmissionproperties for a said second illuminating radiation provided by saidfirst illumination means, and relatively low reflectivity and highoptical transmission properties for the two said second illuminatingradiations provided by said second illumination means.

The second illumination means may be adapted for providing secondilluminating radiations within said light focusing optics. Inparticular, the second illumination means may be adapted for providingsecond illuminating radiations at an aperture stop plane of said lightfocusing optics. The second illumination means may be provided on abracket having an aperture configured to allow said light beams and saidreturning light beams to pass therethrough without being opticallyaffected by said bracket.

Optionally, the device further comprises:

a first polarizing element located just downstream of said illuminationmeans so as to polarize the light emitted therefrom;

a second polarizing element located just upstream of said firstdetector, wherein said second polarizing element is crossed with respectto the first polarizing element; and

a quarter waveplate at the downstream end of said device.

Further optionally the second illumination means are adapted forselective movement in the depth direction.

The device may comprise a mirror inclined to the optical axis of saidlight focusing optics and having, an aperture configured to allow saidlight beams and said returning light beams to pass therethrough withoutbeing optically affected by said mirror, and wherein said secondillumination means comprises at least one white illumination sourceoptically coupled with suitable color filters, said filters selectivelyproviding illumination radiation in each color in cooperation with saidwhite illumination source, wherein said mirror is coupled to said whiteillumination source to direct radiation therefrom along said opticalaxis. The white illumination source may comprise a phosphorus InGaN LED.The filters may be arranged on sectors of a rotatable disc coupled to amotor, predetermined selective angular motion of said disc selectivelycouples said white illumination source to each said filter in turn.

Optionally, the second illumination means are in the form of suitableLED's, comprising at least one LED for providing illumination radiationin each color. Optionally, the second illumination means are in the formof suitable LED's, comprising at least one white illumination sourceoptically coupled with suitable color filters, said filters selectivelyproviding illumination radiation in each color in cooperation with saidwhite illumination source. The white illumination source may comprise aphosphorus InGaN LED. The filters may be arranged on sectors of arotatable disc coupled to a motor, predetermined selective angularmotion of said disc selectively couples said white illumination sourceto each said filter in turn. The device may further comprise a pluralityof optical fibers in optical communication with said filters and withradiation transmission elements comprised in said second illuminationmeans.

The first detector is adapted for selectively measuring intensity ofeach said second illuminating radiation after reflection from saidportion.

Alternatively, the operation of said imaging means is based onilluminating said portion with substantially white illuminationradiation, and capturing a color image of said portion, wherein saidwhite illuminating radiation is provided in the form of a second arrayof incident light beams transmitted towards the portion along an opticalpath through said probing unit to generate illuminated spots on saidportion along said depth direction, wherein said second array is definedwithin said reference frame. The second array is arranged to providecolor data at a plurality of spatial coordinates substantiallycorresponding to the spatial coordinates of said first array. Theimaging means comprises:—

white illumination radiation means;

second detector having an array of sensing elements for measuringintensity of said white illuminating radiation after reflection fromsaid portion.

Alternatively, the operation of said imaging means is based onilluminating said portion with substantially white illuminationradiation, selectively passing radiation reflected from said portionthrough a number of color filters, capturing a monochromatic image ofsaid portion corresponding to each said filter, and combining themonochromatic images to create a full color image, wherein saidilluminating radiation is provided in the form of a second array ofincident light beams transmitted towards the portion along an opticalpath through said probing unit to generate illuminated spots on saidportion along said depth direction, wherein said second array is definedwithin said reference frame. The second array is arranged to providecolor data at a plurality of spatial coordinates substantiallycorresponding to the spatial coordinates of said first array.

Alternatively, the operation of said imaging means is based onilluminating said portion with three differently-colored illuminationradiations, capturing a monochromatic image of said portioncorresponding to each said illuminating radiation, and combining themonochromatic images to create a full color image, wherein each saidilluminating radiation is provided in the form of a second array ofincident light beams transmitted towards the portion along an opticalpath through said probing unit to generate illuminated spots on saidportion along said depth direction, wherein said second array is definedwithin said reference frame, and wherein said illuminating radiationsare provided by said first illumination source. The second array isarranged to provide color data at a plurality of spatial coordinatessubstantially corresponding to the spatial coordinates of said firstarray.

The device may further comprise a tri-color sequence generator forcontrolling the illumination of said portion with said secondilluminating radiations.

The device further comprises a processor coupled to said detector forconformally mapping color data provided by said imaging means to saiddepth data provided by said scanning means for each said spatialcoordinates of said first array to provide a color three-dimensionalnumerical entity comprising a plurality of data points, each data pointcomprising three-dimensional surface coordinate data and color dataassociated therewith. The device may also optionally comprise a unit forgenerating manufacturing data for transmission to CAD/CAM device basedon said entity, and a communication port of a communication medium.

The device is adapted for determining color and surface topology of ateeth portion, but may be used for determining color and surfacetopology of any suitable surface.

The present invention is also directed to a method for determining thesurface topology and associated color of at least a portion of a threedimensional structure, comprising:

(a) providing depth data of said portion corresponding to atwo-dimensional reference array substantially orthogonal to a depthdirection;

(b) providing two-dimensional image data of said portion associated withsaid reference array;

(c) ensuring that a spatial disposition with respect to said portionduring steps (a) and (b) is substantially fixed;

(d) conformally mapping said color data to said depth data for saidreference array.

Preferably, in step (c), a minimum time interval is allowed betweenacquisition of said depth data and acquisition of said image data. Thetime interval may be between about 0 seconds to about 100 milliseconds,preferably between 0 and 50 milliseconds, and more preferably between 0and 20 milliseconds.

In described embodiments, the depth data is provided using confocalimaging techniques. The method can then comprise:

(i) providing a first array of incident light beams defined within saidreference array propagating in an optical path leading through afocusing optics and through a probing face; the focusing optics definingone or more focal planes forward said probing face in a positionchangeable by said optics, each light beam having its focus on one ofsaid one or more focal plane; the beams generating a plurality ofilluminated spots on the structure;

(ii) detecting intensity of returned light beams propagating from eachof these spots along an optical path opposite to that of the incidentlight;

(iii) repeating steps (i) and (ii) a plurality of times, each timechanging position of the focal plane relative to the structure;

(iv) for each of the illuminated spots, determining a spot-specificposition, being the position of the respective focal plane yielding amaximum measured intensity of a respective returned light beam; and

(v) generating data representative of the topology of said portion.

Step (ii) may be based on illuminating said portion with at least threedifferently-colored illumination radiations, said illuminationradiations being combinable to produce white radiation, capturing amonochromatic image of said portion corresponding to each saidilluminating radiation, and combining the monochromatic images to createa full color image, wherein each said illuminating radiation is providedin the form of a second array of incident light beams transmittedtowards the portion along an optical path through said probing unit togenerate illuminated spots on said portion along said depth direction,wherein said second array is defined within said reference frame. Thesecond array is arranged to provide color data at a plurality of spatialcoordinates substantially corresponding to the spatial coordinates ofsaid first array.

Optionally, the sources for the at least three colored illuminations maybe located at the confocal system aperture stop, and facing theobjective lens of the system. Preferably, the illumination sources areconfigured to have a relatively low numerical aperture compared withthat of the first array of light beams. Further preferably, the confocalsystem is configured for chromatically dispersing said coloredilluminations therethrough.

Preferably, the method further comprises providing an improved focus 2Dcolor image of said structure, comprising:—

(I) sequentially illuminating the structure with each one of a pluralityof illuminations, each said illumination having a different wavelengthin the visible spectrum;

(II) providing a monochrome image of the structure when illuminated witheach illumination in (I);

(III) manipulating image data obtained in (II) to provide a best focuscomposite image;

(IV) manipulating image data in (II) and (III) to provide a compositefocused color image of the structure.

Further preferably, the said sources for the colored illuminations aremoveable in the depth direction.

Optionally, the method of the invention further comprises the steps of:

polarizing the emitted colored illuminations by means of a firstpolarizing element;

modifying the said polarized color illuminations on the way to thestructure and on their return therefrom by means of a quarter waveplate;

causing the returning color illuminations to pass through a secondpolarizing element located just upstream of said first detector, whereinsaid second polarizing element is crossed with respect to the firstpolarizing element.

Step (ii) may be based on illuminating said portion with substantiallywhite illumination radiation, selectively passing radiation reflectedfrom said portion through a number of color filters, capturing amonochromatic image of said portion corresponding to each said filter,and combining the monochromatic images to create a full color image,wherein said illuminating radiation is provided in the form of a secondarray of incident light beams transmitted towards the portion along anoptical path through said probing unit to generate illuminated spots onsaid portion along said depth direction, wherein said second array isdefined within said reference frame. The second array is arranged toprovide color data at a plurality of spatial coordinates substantiallycorresponding to the spatial coordinates of said first array.

Step (ii) may be based on illuminating said portion with threedifferently-colored illumination radiations, capturing a monochromaticimage of said portion corresponding to each said illuminating radiation,and combining the monochromatic images to create a full color image,wherein each said illuminating radiation is provided in the form of asecond array of incident light beams transmitted towards the portionalong an optical path through said probing unit to generate illuminatedspots on said portion along said depth direction, wherein said secondarray is defined within said reference frame, and wherein saidilluminating radiations are provided by said first illumination source.The second array is arranged to provide color data at a plurality ofspatial coordinates substantially corresponding to the spatialcoordinates of said first array.

The data representative of said topology may be used for constructing anobject to be fitted within said structure, or may be converted into aform transmissible through a communication medium to recipient.Typically, the structure is a teeth segment. The structure may be ateeth segment with at least one missing tooth or a portion of a toothand said object is said at least one missing tooth or the portion of thetooth. Thus, for example, steps (i) to (v) may be repeated for twodifferent surfaces of said structure to provide surface topologiesthereof, and the surface topologies may then be combined to obtain colorand topological data representative of said structure.

The method of the invention, and also the operation of the device of thepresent invention, may be modified to take account of any possiblerelative movement between the device and the intra oral cavity, forexample as follows: —

(a) providing depth data of said portion corresponding to atwo-dimensional reference array substantially orthogonal to a depthdirection;

(b) providing two-dimensional image data of said portion associated withsaid reference array;

(c) repeating step (a);

(d) for each image color data point obtained in step (b), i.e., for eachparticular (x, y) point on the array for which a color value wasobtained in step (b), providing an estimated value for depth, based onthe depth values obtained in steps (a) and (c) for the same part of thearray, i.e. based on the Z-values obtained for the same (x, y) point insteps (a) and (c). The estimated value may be based on a simplearithmetic mean, on a weighted mean, or on any suitable empirical ortheoretical formula, algorithm and so on.

Of course, step (a) may be repeated a number of times consecutivelybefore step (b), and optionally also after step (b), the time intervalsbetween each step being taken. In any case, for each point on the array(x, y), the values of depth Z may be plotted against elapsed time, forsteps (a) (single or repeated), through step (b) and steps (c) (singleor repeated), and the best estimate of the value of Z corresponding tothe time interval when step (b) was carried out can be calculated,using, for example, any suitable interpolation or curve-fitting method.

Alternatively, the method of the invention, and thus the operation ofthe device of the present invention, may be modified to take account ofany possible relative movement between the device and the intra oralcavity, for example as follows:

(a) providing two-dimensional image data of said portion associated withsaid reference array;

(b) providing depth data of said portion corresponding to atwo-dimensional reference array substantially orthogonal to a depthdirection;

(c) repeating step (a);

(d) for each depth data point obtained in step (b), i.e., for eachparticular (x, y) point on the array for which a depth value wasobtained in step (b), providing an estimated value for color, based onthe color values obtained in steps (a) and (c) for the same part of thearray, i.e. based on the C-values obtained for the same (x, y) point insteps (a) and (c). The estimated value may be based on a simplearithmetic mean, on a weighted mean, or on any suitable empirical ortheoretical formula, algorithm and so on.

Of course, step (a) may optionally be repeated a number of timesconsecutively before step (b), and optionally also after step (b), thetime intervals between each step being taken. In any case, for eachpoint on the array (x, y), the values of color C may be plotted againstelapsed time, for steps (a) (single or repeated), through step (b) andsteps (c) (single or repeated), and the best estimate of the value of Ccorresponding to the time interval when step (b) was carried out can becalculated, using, for example, any suitable interpolation orcurve-fitting method.

Optionally, the steps of providing color values and depth values may berepeated in any sequence, for example in alternate sequence, and asuitable color value may be associated with a corresponding depth value,similarly to the manner described above, mutatis mutandis.

The invention also relates to a method for reconstruction of color andtopology of a three-dimensional structure comprising:

determining surface topologies from at least two different positions orangular locations relative to the structure, by the method of theinvention described above;

combining the surface topologies to obtain color and topological datarepresentative of said structure.

The method may be applied to the reconstruction of topology of a teethportion, and comprise the steps:

determining surface topologies of at least a buccal surface and alingual surface of the teeth portion;

combining the surface topologies to obtain data representative of athree-dimensional structure of said teeth portion.

The method may be applied to obtaining data representative of athree-dimensional structure of a teeth portion with at least one missingtooth or a portion of a tooth.

The data may be used in a process of designing or manufacturing of aprostheses of said at least one missing tooth or a portion of a tooth.Such a prosthesis may be, for example, a crown, a bridge, a dentalrestoration or a dental filing.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

In order to understand the invention and to see how it may be carriedout in practice, a number of embodiments will now be described, by wayof non-limiting example only, with reference to the accompanyingdrawings, in which:

FIG. 1 illustrates the main elements of preferred embodiments of theinvention.

FIGS. 2A, 2B, 2C graphically illustrates the creation of a threedimensional color entity from a three dimensional monochrome entity anda two dimensional color entity.

FIG. 3 graphically illustrates an alignment procedure according to theinvention for aligning the X-Y coordinates of a three dimensionalmonochrome entity with corresponding coordinates of a two dimensionalcolor entity.

FIGS. 4A and 4B schematically illustrate the main elements of a portionof the invention used for providing a three dimensional monochromeentity.

FIGS. 5A, 5B, 5C illustrate in plan view, side view and isometric view,respectively, a probe used in first embodiment of the invention toprovide a two dimensional color entity.

FIG. 6 illustrates in side view a sheath for a probe used in secondembodiment of the invention to provide a two dimensional color entity.

FIG. 7A illustrates in side view a probe used in third embodiment of theinvention to provide a two dimensional color entity. FIG. 7B illustratesthe transmission and reflection characteristics of a typical dichroiccoating used in the probe of FIG. 7A:

FIG. 8 illustrates in side view the general arrangement of the mainelements used in fourth embodiment of the invention to provide a twodimensional color entity.

FIG. 9 illustrates an LED arrangement used with the embodiment of FIG.8.

FIG. 10 illustrates an alternative illumination arrangement used withthe embodiment of FIG. 8. FIG. 10A illustrates details of the tri-colordisc used with the illumination arrangement of FIG. 10.

FIG. 11 illustrates in side view the general arrangement of the mainelements used in fifth embodiment of the invention to provide a twodimensional color entity.

FIG. 12 illustrates in side view the general arrangement of the mainelements used in sixth embodiment of the invention to provide a twodimensional color entity.

FIG. 13 illustrates in side view the general arrangement of the mainelements used in seventh embodiment of the invention to provide a twodimensional color entity.

DETAILED DESCRIPTION OF THE INVENTION

Reference is first being made to FIG. 1 which illustrates the generalrelationship between the various elements of the device of theinvention, generally designated with the numeral 100, according to theembodiments described herein.

The device 100 comprises a main illumination source 31 for illuminatingthe object of interest 26, typically a part of the intraoral cavity, andis optically coupled to main optics 41 to provide depth Z values for anarray range of X-Y points (according to a known frame of reference)along the surface of the object 26. Detection optics 60 comprises animage sensor, typically a CCD, that is preferably monochromatic tomaximise the resolution of the device, and which typically defines theX-Y frame of reference. Alternatively, the CCD may be adapted to receivecolor images. The detection optics 60 receives image data from the mainoptics 41 and the image processor 24 determines the depth Z values foreach X-Y point illuminated on the object 26 based on this image data. Inthis manner, a manipilable three-dimensional numerical entity Ecomprising the surface coordinates of the object 26.

The device 100 further comprises color illuminating means, such as forexample a tri-color sequence generator 74, for selectively illuminatingthe object 26 with suitable colors, typically Green, Red and Blue, andfor each such monochromatic illumination, a two dimensional image of theobject 26 is captured by the detection optics 60. The processor 24 thenprocesses the three differently colored monochromatic images andcombines the same to provide a full color 2D image of the object. Thedevice 100 is configured for providing color data for an array of X-Ypoints that is according to the same frame of reference as the X-Y arrayused for obtaining the 3D entity.

The processor 24 aligns the 2D color image with the 3D entity previouslycreated, and then provides color values to this entity by mapping colorvalues to the entity at aligned X-Y points. Such alignment isstraightforward because both the 3D data and the 2D color data arereferenced to the same X-Y frame of reference. Referring to FIGS. 2A,2B, 2C, the mapping procedure is performed as follows. Athree-dimensional numerical entity E is obtained by-determining depthZ-values for a grid of X-Y points, illuminated via main optics 41 anddetermined by image processor 24. The entity E thus comprises an arrayof (X, Y, Z) points, as illustrated in FIG. 2A. The X-Y plane of entityE is substantially parallel to the sensing face of the image sensingmeans of the detection optics 60, typically a CCD. Almost concurrently,i.e., either just before or just after the readings for determining the3D entity E are obtained by the detection optics 60, a 2D color image ofthe object 26 is taken using the same detection optics 60, atsubstantially the same relative spatial disposition between thedetection optics 60 and the object 26, FIG. 2B. If a monochromatic CCDis used, the 2D color image obtained is a composite created from threeseparate monochromatic images, each provided by illuminating the object26 with a different color, such as for example red, green and blue. The2D color image thus corresponds to another entity N comprised of thelocation and color value of each pixel forming this image, (X′, Y′, C).The X′-Y′ coordinates' of the pixels are on a plane substantiallyparallel to the X-Y plane of the entity E, and furthermore thesecoordinates represent substantially the same part of the object 26 asthe X-Y coordinates of entity E. The reason for this is that the opticalinformation that is used for creating both the 3D entity E and the color2D entity N are obtained almost simultaneously with a very small timeinterval therebetween, and typically there is insufficient time for anysignificant relative movement between the image plane of the detectionoptics 60 and the object 26 to have occurred between the two scans.Thus, similar X-Y and X′-Y′ coordinates in the entities E and N,respectively, will substantially represent the same part of the object26. Accordingly, the color value C of each pixel of entity N can bemapped to the data point of entity E having X-Y coordinates that are thesame as the X′-Y′ coordinates of the pixel, whereby to create anotherentity I comprising surface coordinate and color data, (X, Y, Z, C), asillustrated in FIG. 2C.

Were the relative angle and disposition between the plane of the sensingface of the detection optics 60 with respect to the object 26 changesignificantly between the 2D and the 3D scans, then the X-Y coordinatesof entity E having similar values to the X′-Y′ coordinates of entity Ncould correspond to different parts of the object 26, and thus it maythen be difficult to map the color values of entity N to entity E.However, if only a small movement between the detection optics 60 withrespect to the object 26 occurs, particularly involving a relativetranslation or a rotation about the depth direction (Z), butsubstantially no change in the angular disposition between detectionoptics 60 and the object 26 about the X or Y axes, it may still bepossible to map the color values of entity N to entity E, but first analignment procedure must be followed.

Referring to FIG. 3, such an alignment procedure may be based on opticalcharacter recognition (OCR) techniques. In the X-Y plane, the X-Ycoordinates of entity E can be divided up into two groups, one groupcomprising Z values corresponding to the depth of the object, and asecond group for which no reasonable Z value was found and this groupcorresponds to the background relative to object 26. The profiles ofshapes represented by the X-Y coordinates of the first group of entityE, herein referred to as another entity E′, are then optically comparedwith profiles of shapes corresponding to the X′-Y′ coordinates of entityN, herein referred to as another entity N′. Accordingly, entity E′ istranslated or rotated (coplanarly) with respect to entity N′ until abest fit between the optical shapes between the two entities isobtained, using OCR techniques that are well known in the art.Typically, the image processor, or another computer, will attempt toalign the outer border of the object 26 as seen along the Z-axis andencoded in entity E with optical elements in the 2D color image encodedin entity N. Thereafter, the color value C of each X′-Y′ coordinate ofentity N is mapped to the appropriate data point of entity E having thealigned X-Y coordinates corresponding thereto. The color mappingoperation to create entity I may be executed by any suitablemicroprocessor means, typically processor 24 of the device 100 (FIG.4B).

The main optics 41, main illumination source 31, detection optics 60 andimage processor 24 are now described with reference to FIGS. 4A and 4Bwhich illustrate, by way of a block diagram an embodiment of a system 20for confocal imaging of a three dimensional structure according to WO00/08415 assigned to the present assignee, the contents of which areincorporated herein. Alternatively, any suitable confocal imagingarrangement may be used in the present invention.

The system 20 comprises an optical device 22 coupled to a processor 24.Optical device 22 comprises, in this specific embodiment, asemiconductor laser unit 28 emitting a laser light, as represented byarrow 30. The light passes through a polarizer 32 which gives rise to acertain polarization of the light passing through polarizer 32. Thelight then enters into an optic expander 34 which improves the numericalaperture of the light beam 30. The light beam 30 then passes through amodule 38, which may, for example, be a grating or a micro lens arraywhich splits the parent beam 30 into a plurality of incident light beams36, represented here, for ease of illustration, by a single line. Theoperation principles of module 38 are known per se and the art and theseprinciples will thus not be elaborated herein.

The optical device 22 further comprises a partially transparent mirror40 having a small central aperture. It allows transfer of light from thelaser source through the downstream optics, but reflects lighttravelling in the opposite direction. It should be noted that inprinciple, rather than a partially transparent mirror other opticalcomponents with a similar function may also be used, e.g. a beamsplitter. The aperture in the mirror 40 improves the measurementaccuracy of the apparatus. As a result of this mirror structure thelight beams will yield a light annulus on the illuminated area of theimaged object as long as the area is not in focus; and the annulus willturn into a completely illuminated spot once in focus. This will ensurethat a difference between the measured intensity when out-of- andin-focus will be larger. Another advantage of a mirror of this kind, asopposed to a beam splitter, is that in the case of the mirror internalreflections which occur in a beam splitter are avoided, and hence thesignal-to-noise ratio improves.

The unit further comprises a confocal optics 42, typically operating ina telecentric mode, a relay optics 44, and an endoscopic probing member46. Elements 42, 44 and 46 are generally as known per se. It shouldhowever be noted that telecentric confocal optics avoidsdistance-introduced magnification changes and maintains the samemagnification of the image over a wide range of distances in the Zdirection (the Z direction being the direction of beam propagation). Therelay optics enables to maintain a certain numerical aperture of thebeam's propagation.

The endoscopic probing member 46 typically comprises a rigid,light-transmitting medium, which may be a hollow object defining withinit a light transmission path or an object made of a light transmittingmaterial, e.g. a glass body or tube. At its end, the endoscopic probetypically comprises a mirror of the kind ensuring a total internalreflection and which thus directs the incident light beams towards theteeth segment 26. The endoscope 46 thus emits a plurality of incidentlight beams 48 impinging on to the surface of the teeth section.

Incident light beams 48 form an array of light beams arranged in an X-Yplane, in the Cartesian frame 50, propagating along the Z axis. As thesurface on which the incident light beams hits is an uneven surface, theilluminated spots 52 are displaced from one another along the Z axis, atdifferent (X_(i), Y_(i)) locations. Thus, while a spot at one locationmay be in focus of the optical element 42, spots at other locations maybe out-of-focus. Therefore, the light intensity of the returned lightbeams (see below) of the focused spots will be at its peak, while thelight intensity at other spots will be off peak. Thus, for eachilluminated spot, a plurality of measurements of light intensity aremade at different positions along the Z-axis and for each of such(X_(i), Y_(i)) location, typically the derivative of the intensity overdistance (Z) will be made, the Z, yielding maximum derivative, Z₀, willbe the in-focus distance. As pointed out above, where, as a result ofuse of the punctured mirror 40, the incident light forms a light disk onthe surface when out of focus and a complete light spot only when infocus, the distance derivative will be larger when approaching in-focusposition thus increasing accuracy of the measurement.

The light scattered from each of the light spots includes a beamtravelling initially in the Z-axis along the opposite direction of theoptical path traveled by the incident light beams. Each returned lightbeam 54 corresponds to one of the incident light beams 36. Given theunsymmetrical properties of mirror 40, the returned light beams arereflected in the direction of the detection optics 60. The detectionoptics 60 comprises a polarizer 62 that has a plane of preferredpolarization oriented normal to the plane polarization of polarizer 32.The returned polarized light beam 54 pass through an imaging optic 64,typically a lens or a plurality of lenses; and then through a matrix 66comprising an array of pinholes. CCD camera has a matrix or sensingelements each representing a pixel of the image and each onecorresponding to one pinhole in the array 66.

The CCD camera is connected to the image-capturing module 80 ofprocessor unit 24. Thus, each light intensity measured; in each of thesensing elements of the CCD camera is then grabbed and analyzed, in amanner to be described below, by processor 24.

Unit 22 further comprises a control module 70 connected to a controllingoperation of both semi-conducting laser 28 and a motor 72. Motor 72 islinked to telecentric confocal optics 42 for changing the relativelocation of the focal plane of the optics 42 along the Z-axis. In asingle sequence of operation, control unit 70 induces motor 72 todisplace the optical element 42 to change the focal plane location andthen, after receipt of a feedback that the location has changed, controlmodule 70 will induce laser 28 to generate a light pulse. At the sametime, it will synchronize image-capturing module 80 to grab datarepresentative of the light intensity from each of the sensing elements.Then in subsequent sequences the focal plane will change in the samemanner and the data capturing will continue over a wide focal range ofoptics 44.

Image capturing module 80 is connected to a CPU 82, which thendetermines the relative intensity in each pixel over the entire range offocal planes of optics 42, 44. As explained above, once a certain lightspot is in focus, the measured intensity will be maximal. Thus, bydetermining the Z, corresponding to the maximal light intensity or bydetermining the maximum displacement derivative of the light intensity,for each pixel, the relative position of each light spot along theZ-axis can be determined. Thus, data representative of thethree-dimensional pattern of a surface in the teeth segment, can beobtained. This three-dimensional representation may be displayed on adisplay 84 and manipulated for viewing, e.g. viewing from differentangles, zooming-in or out, by the user control module 86 (typically acomputer keyboard).

The device 100 further comprises means for providing a 2D color image ofthe same object 26, and any suitable technique may be used for providingthe color image. A number of such techniques are described below.

The first technique is based on illuminating the object 26 sequentiallywith three different colored lights such as red, green and blue, andcapturing a monochromatic image corresponding to each color via CCD 68and the image capture device 80 (see FIGS. 4A, 4B). Referring to FIG. 1,tri-color light sources 71, i.e., one or more light sources that provideilluminating radiations to the object 26 in a plurality of differentcolors, are coupled to a tri-color sequence generator 74, which aresuitably controlled by the processing unit 24 to provide the threecolored illuminations via delivery optics 73 in a predeterminedsequence. The colored illuminations are provided at a relative shorttime interval, typically in the range of about 0 to 100 milliseconds, insome cases being in the order of 50 milliseconds or 20 milliseconds, forexample, with respect to the 3D scan, directly before or after the same.Suitable processing software 82 combines the three images to provide a2D color image comprising an array of data points having location (X, Y)and color (C) information for each pixel of the 2D color image.

According to a first embodiment of the device 100, the delivery optics73 is integral with endoscope 46, which is in the form of a probingmember 90, as illustrated in FIGS. 5A, 5B and 5C. The probing member 90is made of a light transmissive material, typically glass and iscomposed of an anterior segment 91 and a posterior segment 92, tightlyglued together in an optically transmissive manner at 93. Slanted face94 is covered by a totally reflective mirror layer 95. Glass disk 96defining a sensing surface 97 may be disposed at the bottom in a mannerleaving an air gap 98. The disk is fixed in position by a holdingstructure which is not shown. Three light rays are 99 from the mainoptics 42 are represented schematically. As can be seen, they bounce atthe walls of the probing member at an angle in which the walls aretotally reflective and finally bounce on mirror 95 and reflected fromthere out through the sensing face 97. The light rays focus on focusingplane 101, the position of which can be changed by the focusing optics(not shown in this figure). The probe member 90 comprises an interface78 via which optical communication is established with the relay optics44 and the remainder of the, device 100. The probe 90 further comprisesa plurality of tri-color LED's 77, for providing the coloredillumination to the object 26.

The LED's 77 typically comprise different LED's for providing blueradiation and green radiation when red illuminating radiation is used asthe illumination source 31 for the main optics 41 when creating the 3Dentity. Alternatively, if a blue illuminating radiation is used as theillumination source 31, the LED's 77 may comprise green and red LED's,and if a green illuminating radiation is used as the illumination source31, LED's 77 may comprise blue and red LED's.

The tri-color LED's 77 are each capable of providing an illuminationradiation in one of three colors, typically red, green or blue, ascontrolled via the tri-color sequence generator. Alternatively, aplurality of LED's in three groups, each group providing illumination inone of the desired colors, may be provided. The LED's 77 are located atthe periphery of the interface 78 such that the LED's do not interferewith the other optical operations of the device 100. In particular suchoperations include the transmission of the illuminating radiation forthe confocal focusing operations, and also the transmission of reflectedlight from the object 26 to the main optics 41 to provide the 3D entityor the 2D color entity. The LED's are mounted substantially orthogonallywith respect to the interface 78, and thus, as illustrated in FIG. 5C,light from each of the LED's 77 is transmitted by internal reflectionwith respect to the walls of the probe 90, to the user interface end 79of the probe.

Preferably, the device 100 according to a variation of the firstembodiment is further adapted for providing improved precision of thecolor data obtained therewith, in a similar manner to that describedherein for the fourth embodiment, mutatis mutandis.

According to a second embodiment of the device 100, the endoscope 46, isalso in the form of a probing member 90, substantially as described withrespect to the first embodiment, but with the difference that there areno LED's directly mounted thereon at the interface 78, mutatis mutandis.In the second embodiment the delivery optics 73 is in the form of adisposable sleeve, shroud or sheath 190 that covers the outer surfacethe probing member 90, as illustrated in FIG. 6. The sheath 190 is madefrom a waveguiding material, such as an acrylic polymer for example,capable of transmitting an illuminating radiation from the upstream face191 of the sheath 190 therethrough and to the downstream face 192thereto. The upstream face 191 is in the form of a peripheral surfacearound the interface 78. The downstream face 192 is formed as aperipheral projection surrounding a window 193 comprised in said sheath190. The window 193 is in registry with the user interface end 79 of theprobe 90. A plurality of tri-color LED's 177 for providing the coloredillumination to the object 26 are mounted on the device 100 justupstream of the sheath 190. The tri-color LED's 177 are each capable ofproviding an illumination radiation in one of three colors, typicallyred, green or blue, as controlled via the tri-color sequence generator74. Alternatively, a plurality of LED's in three groups, each groupproviding one colored illumination, may be provided. The LED's 177 arelocated outside of the main optics of the device 100, and thus the LED'sdo not interfere with the other optical operations of the device 100 inparticular including the transmission of the illuminating radiation forthe confocal focusing operations, or in the transmission of reflectedlight from the object 26 to provide the 3D entity or the 2D colorentity. The LED's are mounted substantially opposite to the upstreamface 191, and thus, as illustrated in FIG. 6, light from each of theLED's 177 is transmitted by the waveguiding sheath 190 to downstreamface 192 and thence to the object 26. In this embodiment, the sheath 190is particularly useful in maintaining hygienic conditions between onepatient and the next, and avoids the need for sterilizing the probe 90,since the sheath may be discarded after being used with one patient, andreplaced with another sterilised sheath before conducting an intra-oralcavity survey with the next patient.

Preferably, the device 100, according to a variation of the secondembodiment is further adapted for providing improved precision of thecolor data obtained therewith, in a similar manner to that describedherein for the fourth embodiment, mutatis mutandis.

In either one of the first or second embodiments, or variations thereof,a red laser may be used as the illumination source 28 for the mainoptics when creating the 3D entity. As such, this illumination means mayalso be used to obtain the red monochromatic image for the creation ofthe 2D color image, by illuminating the object 26 and recording theimage with the optical detector 60. Accordingly, rather than tri-colorLED's or LED's or three different colors, it is only necessary toprovide LED's adapted to provide only the remaining two colors, greenand blue. A similar situation arises if the illumination source for themain optics 41 is a green or blue laser, wherein illuminating radiationsin only the remaining two colors need to be provided, mutatis mutandis.

In these embodiments, the positioning of the illumination sources at theupstream end of the probe 90 where there is ample room rather than atthe patient interface end 79 where space is tight.

According to a third embodiment of the device 100, the endoscope 46 isalso in the form of a probing member 90, substantially as described withrespect to the second embodiment with the following differences, mutatismutandis. As illustrated in FIG. 7A, in the third embodiment thedelivery optics 73 comprises a plurality of LED's 277 for providing thecolored illumination to the object 26. In this embodiment, a red laseris used as the illumination source for the main optics when creating the3D entity. As such, this illumination means is also used to obtain thered monochromatic image for the creation of the 2D color image. Thus,the LED's 277 are each capable of providing an illumination radiation ineither green or blue, as controlled via the tri-color sequence generator74. The LED's 277 are located on the outer side of slanted face 94, andthus the LED's do not interfere with the other optical operations of thedevice 100 in particular including the transmission of the illuminatingradiation for the confocal focusing operations, or in the transmissionof reflected light from the object 26 to provide the 3D entity or the 2Dcolor entity. The slanted face 94 comprises a dichroic coating 278 onthe outer side thereof, which has relatively high reflectivity and lowtransmission properties with respect to red light, while havingsubstantially high transmission characteristics for blue light and greenlight, as illustrated in FIG. 7B. Thus, as illustrated in FIG. 7A, lightfrom each of the blue or green LED's 277 is transmitted, in turn,through the dichroic coating to interface 79 and thence to the object26, as controlled by the generator 74. At the same time the dichroiccoating permits internal reflection of the red radiation from the mainoptics 41 to the interface 79 and object 26, and thus allows the 3D scanto be completed, as well as allowing the red monochromatic image of theobject 26 to be taken by the device 100. Optionally, rather thanemploying blue and green LED's, tricolor LED's may be used, and properlysynchronized to illuminate with either green or blue light as controlledby generator 74. Alternatively, the illumination source for the mainoptics 41 may be a green or blue laser, in which case the LED's are eachcapable of providing illumination in the remaining two colors, and insuch cases the dichroic coating is adapted for allowing transmission ofthese remaining two colors while providing substantially high reflectionfor the illuminating laser of the main optics, in a similar manner tothat described above for the red laser, mutatis mutandis.

In a fourth embodiment of the device 100, and referring to FIG. 8,tri-color illumination is provided within the main focal optics 42, inparticular at the confocal system aperture stop, and facing theobjective lens of the system. An advantage provided by this form ofillumination is that the tri-color illumination illuminates the object26 through the downstream objective lens 142 in nearly collimated light,and thus the object illumination is highly uniform. The tri-color lightsources 377 may be mounted statically on the physical aperture stop atthe aperture stop plane 150, or alternatively they may be mounted on aretracting aperture stop, which also serves to stop down the systemaperture in preview mode. In this embodiment, by placing the tri-colorlight sources 377 at the aperture stop plane, wherein the light beamfrom the illumination source 31 narrows to a minimum within the mainoptics 41, the external dimensions of the device 100 may still remainrelatively compact.

Referring to FIG. 9, the tri-color light sources 377 may comprise, forexample, a plurality of tri-color LED's 385 mounted onto a bracket 380.The bracket 380 is typically annular, having a central aperture to allowillumination light from the illuminating unit 31 to pass therethroughand to the object 26, and to allow light coming from the object 26 topass therethrough and to the detection optics 60, without being affectedby the bracket 380. At the same time, the bracket 380 positions theLED's in the required location upstream of objective lens 166. The LED'sare arranged in a spaced radial and circumferential manner asillustrated in FIG. 9 to provide the most uniform illumination of theobject 26 possible with this arrangement. Typically, a red laser is usedas the illumination source 31 for the main optics 41 when creating the3D entity. As such, and as in other embodiments, this illumination meansis also used to obtain the red monochromatic image for the creation ofthe 2D color image. Thus, the LED's 385 are each capable of providing anillumination radiation in either green or blue, as controlled via thetri-color sequence generator 74. Alternatively, the illumination sourcefor the main optics 41 may be a green or blue laser, in which case theLED's 385 are each capable of providing illumination in the remainingtwo colors, in a similar manner to that described above for the redlaser, mutatis mutandis. Optionally, rather than employing blue andgreen LED's, tricolor LED's may be used, and properly synchronized toilluminate with either green or blue light as controlled by generator74. Further optionally, the LED's 385 may be used to provide,sequentially, all the required colored illuminations, typically red,green and blue. Alternatively, the LED's 385 each provide illuminationin one of at least three colors. Thus, some of the LED's 385 provide ablue illumination, while other LED's 385 provide green illumination,while yet other LED's 385 provide red illumination.

Preferably, the device 100 according to a variation of the fourthembodiment is further adapted for providing improved precision of thecolor data obtained therewith. In this connection, the device 100according to this variation of the fourth embodiment is adapted suchthat the tri-color light sources 377 each illuminate the object 26 withas wide a depth of field as possible, i.e., at a low numerical aperture.Thus, each set of light sources 377 of the same color, for example blue,illuminates a particular depth of the object 26 in the z-direction whilesubstantially in focus. In contrast, the numerical aperture of theconfocal system itself is relatively high to maximize accuracy of thedepth measurements, and thus provides a relatively narrower depth offield.

Advantageously, the optical system downstream of the light sources 377,in this embodiment the objective lens 166, is chromatic, and inparticular maximizes the chromatic dispersion therethrough.Alternatively or additionally, a chromatic dispersion element, forexample an optically refractive block of suitable refractive index, maybe provided along the optical path between the light sources 377 and theobject 26. Thus, each one of the different-colored light sources 377illuminates a different portion of the object 26 along the z-direction.The light sources 377 providing the blue illumination illuminate infocus a portion of the object 26 closest to the device 100, and thelight sources 377 providing the red illumination illuminate in focus aportion of the object 26 furthest from the device 100. At the same time,the light sources 377 providing the green illumination illuminate infocus a portion of the object 26 intermediate the blue and red portions,and a non-illuminated gap may exists between the red and green, andbetween the green and blue illuminated portions, the depth of these gapsdepending on the dispersion characteristics of the downstream optics.Advantageously, the light sources 377 are also adapted for providingillumination in colors intermediate in wavelengths such as to illuminatethe aforesaid gaps in focus. Thus, the LED's 385 may be adapted forproviding both such additional colored illumination, or some of theLED's 385 may be adapted to provide colored illumination at a firstintermediate wavelength, while another set of LED's 385 may be adaptedto provide colored illumination at a second intermediate wavelength. Forexample, the first intermediate wavelength provides an illumination inaqua, and thus illuminates in focus at least a part of the gaps betweenthe blue and green illuminated focused zones of the object 26, while thesecond intermediate wavelength provides an illumination in amber, andthus illuminates in focus at least a part the gaps between the green andred illuminated focused zones. Of course, additional light sources maybe used to provide further intermediate wavelengths and thus providefurther depth cover illumination, in focus, of the object.

While the device 100 is used as a viewfinder, typically prior to takinga depth and color scan of the object 26, the above arrangement using atleast five different colored illuminations at a low numerical aperture,enables a much clearer and focused real-time color image of the object26 to be obtained. Thus when in operation in viewfinder mode (also knownas “aiming mode”, prior to the 3D scan event, while the dentalpractitioner is in the process of aiming the scanner onto the targetdental surface, for example) the device 100 according to this variationof the fourth embodiment repeatedly illuminates the object 26 in cycles,wherein in each cycle the object 26 is separately illuminated in each ofthe five colors blue, aqua, green, amber, red, in quick succession, andeach time a monochromatic image is obtained by the monochromatic imagesensor in 60. Each set of five monochromatic images is then analysed toprovide a composite color image, and this image is then displayed insubstantially real time in the viewfinder display window in the controlsoftware, so that the succession of such composite images gives theappearance of a substantially real-time color video feed of the object26.

Each of the monochrome images in any particular set corresponds to aparticular illumination color or wavelength, and thus the zone(s) of theobject 26 within the depth of field corresponding to this illuminationwill be in focus, while the other parts of the object 26 will appear outof focus. Thus, each such image in the aforesaid set of images willcontain a portion which has high precision focused image of a part ofthe object, for the particular illumination wavelength.

In forming a composite image for each set of images, the images arecombined in such a way as to maximize the precision of the focused imageand corresponding color thereof. Thus, for example, suitable algorithmsmay be applied to each of the five images of a set to distinguishbetween the focused and unfocused the areas thereof. Such algorithms mayemploy, for example, techniques which apply FFT techniques to areas ofthe images, and which search for high frequency portions whichcorrespond to focused areas. In any case, such algorithms, as well assoftware and hardware to accomplish the same are well known in the art.Then, the focused areas of each of the five images are merged to providea monochrome composite substantially focused image of the object. Next,the images obtained using the red, green and blue illuminations arecombined and converted to a corresponding luminescence/chroma (Y/C)image, and techniques for doing so are well known in the art. Finally,the luminescence component of the luminescence/chroma (Y/C) image isreplaced with the aforesaid corresponding composite focus image, and theresulting new luminescence/chroma image is then transmitted to thedisplay in the viewfinder.

For each set of images, prior to combining the corresponding red, greenand blue images, these are preferably first scaled to compensate formagnification effects of the different wavelengths. Thus, the greenimage, and more so the blue image, needs to be scaled up to match thered image.

When the user is ready to take a depth and color scan of the object 26,having steered the device 100 into position with the aid of theviewfinder, the device 100 takes a depth scan in the z-direction asdescribed herein, and either before or after the same, but in quicksuccession one with the other, takes a color scan in a similar manner tothat described above for the viewfinder mode, mutatis mutandis.Subsequently, the color data and the depth data of the two scans can becombined to provide the full spatial and color data for the surfacescanned.

Advantageously, one or more color scans may also be taken during thedepth scan, and/or at the beginning and at the end of the depth scan. Inone mode of operation, the depth scan is obtained by displacing theobjective lends 166 along the z-direction in a continuous or steppedmotion. Multiple color scans can then be obtained by associating thecolor sources 377 with the objective lens, so that these are alsodisplaced along the z-direction. Accordingly, as the light sources 377are moved in the z-direction towards the object 26 during the depthscan, at each different z-position in which a set of images is taken(concurrently with or alternately with the depth scan), each one of thecolored illuminations—red, green, blue and intermediatewavelengths—illuminates a progressively deeper part of the object alongthe z-direction. Of course, in some cases it is possible that at thedownstream end of the depth scan the green and red illuminationscompletely overshoot the object 26, and the corresponding images may bediscarded or otherwise manipulated to provide a composite color image atthis station. Thus, a plurality of color images can be obtained, eachbased on a different z-position, so that each illumination wavelength isused to illuminate in focus a different part (depth) of the object 26.Advantageously, suitable algorithms may be used to form a compositecolor image of the set of color images associated with a particularz-scan of the object 26 to provide even more precise and accurate colorimage, than can then be combined with the depth data.

Alternatively, and referring to FIG. 10, the tri-color light sources 377may be replaced with a rotating filter illumination system 400. Thesystem 400 comprises a while light source 410, such as for example whitephosphorus InGaN LED's, and the light therefrom is focused onto anoptical fiber bundle 420 by means of condenser optics 430. Between thecondenser optics 430 and the fiber bundle 420 is provided a rotatingtri-color filter 450. As best seen in FIG. 10A, the filter 450 isdivided into three colored sections, comprising blue, green and redfilters on adjacent sectors therein. The fiber bundle 420 is flared atthe downstream end 470 to form the desired illumination pattern.Optionally, the downstream end 470 of the fibers may be mounted onto anannular bracket similar to bracket 380 illustrated in FIG. 9, at theapertures stop plane of the confocal optics. A suitable motor 460,typically a stepper motor for example, drives the rotating filter suchas to sequentially present each colored filter to the light passing fromthe condenser optics 430 to the fiber bundle 420, as synchronized withthe sequence generator 74 (FIG. 1) to enable the detection optics 60 tocapture images of the object 26 when selectively illuminated with eachof the three colors. Optionally, if a red, blue or green illuminatingradiation is used as the illumination source 31 for the main optics 41when creating the 3D entity, then the rotating filter 450 only requiresto comprise the remaining two colors, as discussed above for similarsituations regarding the LED's, mutatis mutandis.

Preferably, the device 100 according to this variation of the fourthembodiment may be further adapted for providing improved precision ofthe color data obtained therewith, in a similar manner to that describedherein for another variation of fourth embodiment, mutatis mutandis. Inparticular, the filter 450 is divided into five (or more if desired)colored sections, comprising blue, aqua, green, amber and red filters onadjacent sectors therein.

A fifth embodiment of system 100 is substantially similar to the fourthembodiment as described herein, with the following difference, mutatismutandis. In the fifth embodiment, and referring to FIG. 11, polarizersare provided at two locations in order to increase the image contrast. Afirst polarizing element 161 is located just downstream of the lightsources 377 so as to polarize the light emitted from the light sources377. A second polarizing element 162 is located just upstream of theimage sensor of the detection optics 60, and is crossed with respect tothe first polarizing element 161. Further, a quarter waveplate 163 isprovided just upstream of the object 26, i.e. at the downstream end ofthe endoscope 46 (FIG. 4A). The first polarizing element 161 istypically annular, having a central aperture to allow illumination lightfrom the illuminating unit 31 to pass therethrough and to the object,and to allow light coming from the object 26 to pass therethrough and tothe detection optics 60, without being affected by the polarizingelement 161. However, light that is reflected from the object 26 returnsto the main confocal optics 42 in a crossed polarization state due tothe effect of the quarter waveplate 163, and thus reaches the detectionoptics 60 at substantially full intensity. However, any light reflectedfrom the objective lens 166 of the confocal optics 42 is reflected atthe same polarization state, and is therefore filtered out by thecrossed polarizing element 162. This arrangement serves as an effectivesignal to ghost enhancement system.

Preferably, the device 100 according to a variation of the fifthembodiment is further adapted for providing improved precision of thecolor data obtained therewith, in a similar manner to that describedherein for the fourth embodiment, mutatis mutandis.

A sixth embodiment of the system 100 is substantially as described forthe fourth embodiment, with the following difference, mutatis mutandis.In the sixth embodiment, and referring to FIG. 12, the tri-color lightsources 377 are replaced with a rotating filter illumination system 500.The system 500 comprises a while light source 510, such as for examplewhite phosphorus InGaN LED's, and the light therefrom is focused onto amirror 520 by means of condenser optics 530. Between the condenseroptics 530 and the mirror 520 is provided a rotating tri-color filter550, which is similar to the filter 450 illustrated in FIG. 11, and thuscomprises three colored sections, comprising blue, green and red filterson adjacent sectors therein, and is actuated by motor 560. The opticalaxis OA of the confocal optics 41 is orthogonal to the optical axis OA′of the light source 510 and condenser optics 530. The mirror 520 ismounted between the aperture stop plane and the objective lens 166 ofthe confocal optics, and at an angle to the optical axis OA thereof andto the optical axis OA′ of the light source 510 and condenser optics530. The mirror 520 is typically annular, having a central aperturealigned with optical axis OA to allow illumination light from theilluminating unit 31 to pass therethrough and to the, object 26, and toallow light coming from the object 26 to pass therethrough and to thedetection optics 60, without being affected by the mirror 520. At thesame time, the mirror 520 has sufficient reflecting surface to reflectlight from the source 510 via objective lens 166 and to the object 26.Optionally, if a red, blue or green illuminating radiation is used asthe illumination source 31 for the main optics 41 when creating the 3Dentity, then the rotating filter 550 only requires the remaining twocolors, as discussed above for similar situations, mutatis mutandis.

Preferably, the device 100 according to a variation of the sixthembodiment is further adapted for providing improved precision of thecolor data obtained therewith, in a similar manner to that describedherein for the fourth embodiment, mutatis mutandis.

According to a second technique for providing the aforesaid 2D colorimage, the object 26 is illuminated with a white light, and a color CCDis used for receiving the light reflected from the object 26. Thus, aseventh embodiment of the system 100 comprises a white lightillumination system 600, illustrated in FIG. 13. The system 600comprises a while light source 610, such as for example white phosphorusInGaN LED's, and the light therefrom is directed onto a flip mirror 620via a polarizing beam splitter 650 by means of condenser optics 630. Theoptical axis OA of the confocal optics 41 is orthogonal to the opticalaxis OA″ of the light source 610 and condenser optics 630. The mirror620 is mounted between the aperture stop plane 155 and the objectivelens 166 of the confocal optics, and at an angle to the optical axis OAthereof and to the optical axis OA″ of the light source 610 andcondenser optics 630.

The mirror 620 is adapted to flip away from optical axis OA when thedevice 100 is being used for obtaining the 3D entity E. This allowsillumination light from the illuminating unit 31 to pass therethroughand to the object 26, and to allow light coming from the object 26 topass therethrough and to the detection optics 60, without being affectedby the mirror 620. When it is desired to take a 2D color image, themirror 620 is flipped down to the position shown in FIG. 13. Polarizingbeam splitter 650 that polarizes white light from the source 610 andallows the same to pass therethrough and to mirror 620, and thence tothe object 26 via the confocal objective 166 and broadband quarter waveplate 163. Light that is reflected from the object 26 returns to themirror 620 in a crossed polarization state due to the effect of thequarter waveplate 163, and thus reaches the color CCD 660 (andassociated detection optics—not shown) at substantially full intensity.However, any light reflected from the objective lens 166 of the confocaloptics 42 is reflected at the same polarization state, and is thereforefiltered out by a crossed polarizing element 662 just upstream of theCCD 660. This arrangement serves as an effective signal to ghostenhancement system.

Alternatively, the CCD of the detection optics 60 is a color CCD and isalso used for the 2D scan. In such a case, flipping mirror 620 isreplaced with a fixed mirror having a central aperture similar to mirror520, having a central aperture, as described for the sixth embodiment,mutatis mutandis.

In the seventh embodiment, the image capture device 80 and processingsoftware 82 (FIG. 4 b) automatically provide a 2D color image comprisingan array of data points having location (X, Y) and color (C) informationfor each pixel of the image.

According to a third technique for providing the 2D color image, theobject is illuminated with a white light, and the light reflected fromthe object 26 is passed sequentially through one of three differentcolored filters such as red, green and blue. Each time a monochromaticimage corresponding to each color is captured via CCD 68 and the imagecapture device 80 (see FIGS. 4A, 4B). Suitable processing software 82combines the three images to provide a 2D color image comprising anarray of data points having location (X, Y) and color (C) informationfor each pixel of the image.

According to a fourth technique for providing the color image, the mainillumination source 31 of device 100 comprises suitable means forproviding the three different colored illuminations. In one embodiment,the illumination source 31 comprises three different lasers, each oneproviding an illumination radiation at a different desired color, redgreen or blue. In another embodiment, a suitable white lightillumination means is provided, coupled to a suitable rotating tri-colorfilter, similar to the filters described above, mutatis mutandis. Ineach case, suitable control means are provided, adapted to illuminatethe object 26 with each colored radiation in turn, and the 2D coloredimage is obtained in a similar fashion to that described above, mutatismutandis. The object is also illuminated with one of the coloredilluminations in order to provide the 3D surface topology data.

In each of the embodiments described herein, the illumination radiationthat is used for obtaining the 2D color image is injected into theoptical axis OA of the confocal optics 42 without affecting theoperation thereof or degrading the 3D image capture.

The endoscope 46, the illumination unit 31, the main optics 41, colorillumination 71 and tri-color sequence generator are preferably includedtogether in a unitary device, typically a hand-held device. The devicepreferably includes also the detector optics 60, though the latter maybe connected to the remainder of the device via a suitable optical linksuch as a fibre optics cable.

For all embodiments, the data representative of the surface topology andcolor, i.e., entity I, may be transmitted through an appropriate dataport, e.g. a modem 88 (FIG. 4B), through any communication network, e.g.telephone line 90, to a recipient (not shown) e.g. to an off-siteCAD/CAM apparatus (not shown).

By capturing, in this manner, an image from two or more angularlocations around the structure, e.g. in the case of a teeth segment fromthe buccal direction, from the lingual direction and optionally fromabove the teeth, an accurate color three-dimensional representation ofthe teeth segment may be reconstructed. This may allow a virtualreconstruction of the three-dimensional structure in a computerizedenvironment or a physical reconstruction in a CAD/CAM apparatus.

While the present invention has been described in the context of aparticular embodiment of an optical scanner that uses confocal focusingtechniques for obtaining the 3D entity, the device may comprise anyother confocal focusing arrangement, for example as described in WO00/08415. In fact, any suitable means for providing 3D scanning can beused so long as the 3D scan and the color 2D scan correspondsubstantially to the same object or portion thereof being scanned, andthe same frames of references are maintained. Typically the scans areexecuted in relatively quick succession, and by the same or differentimage capturing means such as CCD's that are arranged such that thecolor 2D image substantially corresponds to the 3D entity. This enablescolor values at particular x, y coordinates of the 2D color image to be,matched to the same x, y coordinates of the 3D image which also have a zcoordinate.

The embodiments illustrated herein are particularly useful fordetermining the three-dimensional structure of a teeth segment,particularly a teeth segment where at least one tooth or portion oftooth is missing for the purpose of generating data of such a segmentfor subsequent use in design or manufacture of a prosthesis of themissing at least one tooth or portion, e.g. a crown, or a bridge, or adental restoration or a filing. It should however be noted, that theinvention is not limited to this embodiment, and applies, mutatismutandis, also to a variety of other applications of imaging ofthree-dimensional structure of objects, e.g. for the recordal orarcheological objects, for imaging of a three-dimensional structure ofany of a variety of biological tissues, etc.

While there has been shown and disclosed exemplary embodiments inaccordance with the invention, it will be appreciated that many changesmay be made therein without departing from the spirit of the invention.

In the method claims that follow, alphabetic characters and Romannumerals used to designate claim steps are provided for convenience onlyand do not imply any particular order of performing the steps.

Finally, it should be noted that the word “comprising” as usedthroughout the appended claims is to be interpreted to mean “includingbut not limited to”.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A method for determining the surface topology andassociated color of at least a portion of a three-dimensional dentalstructure, the method comprising: providing a hand-held devicecomprising: (a) a scanning system configured to provide depth data ofthe portion, the depth data corresponding to a plurality of data pointsdefined on a plane substantially orthogonal to a depth direction; (b) animaging system configured to provide color image data of the portionassociated with said plurality of data points; and (c) a processorconfigured to associate the depth data with the color image data,wherein the depth data and the color image data represent the surfacetopology and the color of the portion of the three-dimensional dentalstructure; and operating the hand-held device.
 2. The method accordingto claim 1, wherein the imaging system is configured to provide thecolor image data independently from the depth data.
 3. The methodaccording to claim 1, wherein the plurality of data points is associatedwith a two-dimensional reference array.
 4. The method according to claim1, wherein the operation of the scanning system is based on confocalimaging techniques.
 5. The method according to claim 1, wherein thedepth data and the color image data are associated by aligning theplurality of data points and the color image data in the same frame ofreference.
 6. The method according to claim 5, wherein the frame ofreference comprises a two-dimensional reference array.
 7. The methodaccording to claim 1, wherein the depth data and the color image dataare associated by using an alignment procedure comprising an opticalcharacter recognition technique.
 8. The method according to claim 1,wherein the hand-held device comprises a color illumination systemhaving at least one illumination source configured to transmit lightbeams having different wavelengths in the system.
 9. The methodaccording to claim 8, wherein the depth data and the color image dataare based on measured intensity of the light beams having differentwavelengths.
 10. The method according to claim 8, wherein the colorillumination system comprises three illumination sources configured totransmit light beams independently selected from red, blue and greenlight beams.
 11. The method according to claim 8, wherein the colorillumination system comprises one of the following: (a) a singleillumination source configured to provide three or more illuminationbeams having different wavelengths; or (b) a first illumination sourceconfigured to provide two illumination beams having differentwavelengths, and a second illumination source configured to provide anillumination beam having a different wavelength than the wavelengths ofthe two illumination beams from the first illumination source.
 12. Themethod according to claim 1, wherein the hand-held device comprises: aprobing member having a sensing face; an illumination unit configured totransmit an array of incident light beams towards the three-dimensionaldental structure and through the probing member and the sensing face togenerate illuminated spots on the portion of the structure; an opticalsystem configured to focus the incident light beams at each of aplurality of focal planes located between the sensing face and thestructure; and a detector configured to measure intensity of each of aplurality of returned light beams originating from the illuminatedspots; and wherein the processor is coupled to the detector and isfurther configured to: determine for each of the returned light beams aspot specific position, each spot specific position corresponding to aposition of a respective focal plane in the plurality of focal planes,each respective focal plane corresponding to a maximum intensity of eachrespective returned light beam in the plurality of returned light beams;and generate, based on the determined spot specific positions, datarepresenting the surface topology of the portion of thethree-dimensional dental structure.
 13. The method according to claim12, wherein the array of incident light beams is arranged to providedepth data at a plurality of predetermined spatial coordinates in atwo-dimensional array.
 14. The method according to claim 13, wherein thecolor image data is associated with positions corresponding to thepredetermined spatial coordinates of the two-dimensional array.
 15. Themethod according to claim 1, wherein the processor is further configuredto conformally map the color image data to the depth data to produce acolor, three-dimensional virtual model comprising three-dimensionalsurface topology data associated with color data.
 16. The methodaccording to claim 15, wherein the processor is further configured tooutput the three-dimensional surface topology data associated with colordata to a manufacturing unit configured to manufacture a physical modelof the three-dimensional dental structure based on the color,three-dimensional virtual model.
 17. The method according to claim 1,wherein the three-dimensional dental structure comprises at least aportion of a patient's teeth.
 18. The method according to claim 1,wherein the three-dimensional dental structure comprises at least aportion of a physical model representing a patient's teeth.
 19. Themethod according to claim 1, wherein operating the hand-held devicecomprises generating the depth data of the portion.
 20. The methodaccording to claim 1, wherein operating the hand-held device comprisesgenerating the color image data.
 21. The method according to claim 1,wherein operating the hand-held device comprises generating an imagebased on the depth data and the color image data and representing thesurface topology and the color of the portion of the three-dimensionaldental structure.